In treatment of specific areas or organs of the human body with drugs or other therapeutic substances, it is preferable to provide the therapeutic substance only to the area that needs treatment, rather than delivering the substance generally through the blood stream. Localized delivery of a therapeutic substance avoids any undesirable effects that the substance may have on other areas of the body that do not need treatment. Furthermore, localized delivery provide the intended treatment site with a more concentrated dose of the therapeutic substance because it has not been diluted during its travel through the blood stream. Thus, the treatment can be more effective. An additional benefit of localized delivery is that a reduced quantity of the substance can be used to treat the intended location than would otherwise be required to supply a patient's entire blood stream with a quantity sufficient to create a beneficial concentration of the substance for the intended treatment site. The reduction in required quantity results in substantial savings in cost associated with the treatment, especially where the therapeutic substance is an expensive pharmaceutical.
In treatment of vessels for coronary artery disease, stenosed regions are frequently treated by direct delivery of a therapeutic substance. Commonly, the stenosed area of the vessel is first dilated with an angioplasty balloon catheter prior to or during the delivery of the therapeutic substance. The objective of localized drug treatment of the vessel after angioplasty is to reduce the rate of restenosis, or reclosure of the vessel. Vessels which have undergone angioplasty frequently suffer from restenosis, an abrupt closure of the vessel which quickly blocks the flow of blood and can be fatal. Therefore, drugs such as anti-coagulants are applied to an area of the vessel which has recently undergone angioplasty, usually immediately following the procedure.
A common mechanism for delivering a therapeutic substance to an internal location such as a vessel that has recently undergone angioplasty has been delivery through a porous balloon catheter. Generally, such catheters are configured similar to conventional dilatation balloon catheters with the modification of small holes formed into the balloon through which may flow a therapeutic substance under pressure. The substance is also used as the inflation medium for the balloon. Although the inflated balloon places the perfusion outlets in close proximity to the vessel wall to be treated, expulsion of the therapeutic substance necessarily requires inflation of the balloon, which temporarily blocks the blood vessel being treated. Interruption of blood flow through the vessel is undesirable because it can cause pain and discomfort to the patient. Also, delivery through a porous balloon limits the choice of agents that may be delivered as it is undesirable to mix multiple therapeutic agents within the single inflation lumen and balloon of the delivery catheter.
Variations of the porous balloon concept have been provided in an attempt to address the shortcomings of the porous balloon. Balloons have been disclosed that have multiple lumens extending through or on the balloon wall which contain and perfuse therapeutic substances independent of the inflation medium used to expand the body of the balloon. Some of these devices provides means for delivering more than one substance simultaneously. U.S. Pat. No. 5,713,860 (Kaplan et al.) discloses an infusion catheter having an inflatable member over which may be applied several lumens containing one or more therapeutic substances. Because it is important to present the source of therapeutic substance as close as possible to the intended treatment site, the conduits disclosed in the Kaplan patent are expanded by an inflatable member to be in close proximity to the vessel wall. The inflatable member is provided with slits which form into passageways to permit some blood flow through the area when the member is expanded during drug delivery. However, the inflatable member occupies a sizable cross-sectional area of the vessel when expanded, which may serve to interrupt blood flow during drug delivery.
It would be desirable to provide a device for localized delivery of a therapeutic substance, particularly for use in a vessel, which is configured to permit expansion of delivery conduits into close proximity of or in contact with the treatment site without inflation of a balloon which may serve to restrict blood flow through the treatment area. It is an objective of the present invention to provide such a device.